INSECT POPULATION DYNAMICS AND MANAGEMENT STRATEGIES OF STEMFLY, OPHIOMYIA PHASEOLI (TRYON) (DIPTERA: AGROMYZIDAE) IN SOYBEAN

Abstract

The research work on population dynamics of insects and management strategies of stem fly Ophiomyia phaseoli (Tryon) (Diptera: Agromyzidae) in soybean was carried out at the Breeder Seed Production Center, BARI, Debiganj, Panchagarh, during August 2014 ˗ December 2017. Twenty four insect species were found in soybean field. Of them only eight species were considered as the major pests, while the rests were minor importance on the basis of population density per plant, % infested plant and stem tunneling. The succession of insect pests was found in an overlapping manner and the crop was under continuous attack by one or more pests. Most of the major and minor pests appeared during vegetative and flowering stages (35˗ 45 DAS). The stage of crop had greater influence on the incidence of the pest. Irrespective of sowing times, pest population was first detected from 2nd week after sowing. Cent percent plant became affected at three weeks of plant age. The stem fly infestation was significantly lower in protected plot as compared to unprotected plot. Plant growth, yield and yield contributing parameters were influenced significantly by the pest. The avoidable yield loss was estimated 24.04%. Twelve soybean variety/lines were evaluated to determine their performance for tolerant against stem fly. The lines Culombus and LG-92P-1825 showed the least infestation (47.44, 50.89% plant infestation and 13.33, 14.94% stem tunneling/plant, respectively). The experiment indicated that intercropping of soybean played a vital role against stem fly infestation and yield of soybean. Intercropped soybean with sesame, groundnut and coriander reducing 45.93, 40.42, 39.35% plant infestation and 56.55, 52.14, 44.27% stem tunneling over control, respectively. The highest benefit cost ratio (1.55) was achieved from sesame intercropped plot. The experiment was conducted to develop an effective management of stemfly in soybean using three insecticides and four botanical origins. The results revealed that Carbofuran + Nitro 505 EC (12.33% plant infestation and 5.27% stem tunneling) was the most effective control approach against stemfly. Regarding seed yield, significantly the highest yield (1.97 t/ha) was harvested when Carbofuran (Furadan 5 G) was applied as seed treatment and Nitro spraying but it gave statistically similar result to Nitro (1.92 t/ha) and seed treatment with Carbofuran (1.91 t/ha).